1. Field of the Invention
The present invention relates to a joint structure for antiseismic reinforcement that is applied to a structural member.
2. Description of Background Art
It is known in the background art to reinforce a structure against antiseismic activity. In particular, it is known to use an antiseismic reinforcement member, such as a brace, that is connected at an intersection between a column and beam to reinforce a structure against antiseismic activity.
In the situation where a structure is made of a steel skeleton, a metal fitting for connecting the antiseismic reinforcement member to a column or beam is typically fixed by welding at an intersection between a column and beam on site.
In the situation where a structure is a reinforced concrete structure or a steel skeleton reinforced concrete structure, a steel framework has been used to install the antiseismic reinforcement member.
In addition, other inventions for connecting an antiseismic reinforcement member are known in the background art. For example, a structure that uses a metal fitting to fix an antiseismic reinforcement member to a column of a reinforced concrete structure or a steel skeleton reinforced concrete structure is known in the background art (hereinafter referred to as “background art 1”). The metal fitting is made of a steel plate having a convex cross-section and is fixed using a high-strength fiber sheet.
In addition, a structure that uses a pin fitted into a through-hole formed in a beam to fix an antiseismic reinforcement member to the structure is known in the background art (hereinafter referred to as “background art 2”).
Furthermore, a structure that uses a through-hole formed in a beam and a PC steel rod to fix a pedestal of an antiseismic reinforcement member to the structure is known in the background art (hereinafter referred to as “background art 3”).
In addition, a structure that uses an anchor bolt to fix a metal fitting for connecting an antiseismic reinforcement member to a column and beam, which are made of reinforced concrete, is known in the background art (hereinafter referred to as “background art 4”).
In the situation where welding is used on site to fix a reinforcement member to a steel skeleton structure; however, the following problems may arise:
(1) if an improper condition for welding, such as upward-welding or welding that requires an uncomfortable body position, exists, a welding strength having low reliability may result;
(2) an area around the weld has to be protected by covering with proper materials;
(3) if there is a concrete slab formed on the beam, chipping of the concrete may be required to gain access to the underlying steel; and
(4) in the case of a preexisting building, the chipping of the concrete cannot be carried out while people are living in and using the building because of the significant noise of chipping the concrete, which leads to a longer time of construction.
Also, in the case of a reinforced concrete structure or a steel skeleton reinforced concrete structure, a steel framework has to be set up in a limited space, which also leads to a longer time of construction.
Furthermore, in the case of a steel skeleton reinforced concrete structure, reinforcing bars inside may be an obstacle to using a long anchor.
In the background art 1, the use of a high-strength fiber sheet increases the cost of construction.
In the background art 2, the method may only be applied to an isolated column. Otherwise the construction would have to be extended to an adjacent area.
In the background art 3, a PC steel rod inserted through the beam is used for fixing a pedestal of the antiseismic reinforcement member to the structure. Therefore, it is necessary to drill the concrete slab to form the through-hole. The drilling causes noise and vibration. Also, a concrete strength that matches the tensile force of the PC steel rod is required.
In the background art 4, the method cannot be applied if the concrete is not thick enough.
With regard to the methods according to the background art for setting up a brace as an antiseismic reinforcement member, as mentioned above, there are known methods that fix the brace by welding on site with respect to a steel skeleton structure and fix the brace after installing a steel framework. However the methods according to the background art experience some difficulty in their application, including noise and dust problems.
The inventor of the present invention has proposed a joint structure for an antiseismic reinforcement member, which enables the problems associated with the joint structures in the background arts 1, 2 and 3 to be avoided. In addition, the time of construction and the cost of connecting can be reduced. Furthermore, the area of construction can be limited to the area in question, so that the adjacent area can be used as usual. It is also possible to provide an increased endurance of the joint.
This prior invention from the present inventor can solve the problems of noise and dust, but cannot ensure a large load-bearing. The reasons that this prior invention cannot ensure a large load-bearing is as follows:
(1) the metal fitting part is directly fixed to the slab concrete;
(2) consequently, a tensile force from the antiseismic reinforcement member causes a tensile force in addition to a shearing force to be applied to the concrete slab; and
(3) the concrete slab is locally destroyed at the place where the tensile force is applied.